A wafer processing method includes the following steps: forming, on a back side of a wafer including a device layer, a mask to be used in forming grooves in a substrate along streets from the back side of the wafer; applying plasma etching from the back side of the wafer through the mask to form the grooves in the substrate along the streets; ejecting high-pressure fluid against the back side of the wafer with the wafer mounted at its front side on a mounting surface to press the wafer at regions surrounded by the etched grooves; and bonding a tape to the front side of the wafer before performance of at least the pressing step.